Drafting instrument



9, 1969 P. o. w. HOPK INSON 3,482,318

DRAFTING INSTRUMENT 3 Sheets-Sheet 1 Filed Dec. 23, 1968 Ill 1959 P. o. w. HOPKINSON 3,482,318

DRAFTING INSTRUMENT Filed Dec. 25, 1968 3 Sheets-Sheet k J//{g//////// 5' ATTUR/VEVS.

Dec. 9, 1969 P, o. w. HOPKINSON 3,482,318

DRAFT ING I NSTRUMENT 3 Sheets-Sheet 5 Filed Dec. 23, 1968 w MW.

, INVENTOR. PAUL 0. W. HOP/f/NSO/V GNm United States Patent Office 3,482,318 Patented Dec. 9, 1969 3,482,318 DRAFIING INSTRUMENT Paul O. W. Hopkinson, Gibsonia, Pa., assignor of onehalf to St. Barnabas Free Home, Gibsonia, Pa., a corporation of Pennsylvania Filed Dec. 23, 1968, Ser. No. 786,275 Int. Cl. B431 13/02 U.S. Cl. 33109 9 Claims ABSTRACT OF THE DISCLOSURE Connected with the back end of a stiff base plate there is spring strip means extending forward over the plate. Fastened to the spring strip means is an axle that projects laterally and supports rollers rigidly on its opposite ends. One roller extends slightly below the base plate to space the plate from a surface supporting the rollers. A straightedge member extends across the front of the plate, to which it is connected. The bottoms of the plate and straight-edge member normally slope downward and forward relative to the supporting surface but can be pressed down flat on that surface when the spring strip means is pressed down.

It is among the objects of this invention to provide a drafting instrument with which parallel lines can be drawn very rapidly, and which is simple in construction and easy to use.

The invention is illustrated in the accompanying drawings in which FIG. 1 is a plan view;

FIG. 2 is a rear view;

FIG. 3 is an enlarged end view;

FIG. 4 is an enlarged cross section taken on the line IVIV of FIG. 1, but showing the instrument pressed down on a supporting surface;

FIG. 5 is a plan view of a modification;

FIG. 6 is a rear view; and

FIGS. 7 and 8 are enlarged views, corresponding to FIGS. 3 and 4, of the modification.

Referring to FIGS. 1, 2 and 3 of the drawings, a small rectangular base plate 1 with a fiat bottom has screws 2 extending upwardly through it near its back corners. Encircling each of these screws is a hollow post 3, on which the rear end of spring strip means, such as a rectangular metal leaf spring 4, is mounted. The spring is clamped down on the post by means of nuts 5 on the upper ends of the screws. The spring extends forward over the base plate but terminates behind the front end of the plate. The front end of the spring overlies the central portion of a tube 6, to which it is fastened by screws 7. The tube projects laterally from the opposite sides of the spring. Rotatably mounted in this tube is an axle 8 that has ends projecting from the tube. Mounted tightly on each of these ends and up against the adjoining end of the tube is a roller 9 provided with a narrow surface that is knurled to provide a high coefficient of friction with the surface on which it rolls. The roller normally extends a slight distance below the base plate in order to space it from the surface supporting the roller. This would normally be a sheet of drawing paper on a drawing board.

A straight-edge member 11 extends across the front end of the base plate and laterally from it. This member preferably is a rigid transparent plastic strip of uniform width several inches long. The back of the strip is joined to the front end of the base plate. Preferably, this is a detachable connection formed by a splice plate 12 that is integral with or secured to the straight-edge strip and projects rearwardly over the front end of the base plate. The projection portion of the spliced plate is provided with a notch 13 that fits around a screw 14 threaded in the base plate and extending upwardly to a level above the leaf spring. The portion of the screw directly above the base plate has a smaller diameter than the portion above it so that the screw has a shoulder 15 that clamps down on the spliced plate on opposite sides of its notch when the screw is tightened. When the straight-edge is properly fastened to the base plate by screw 14, the front edge of the straight-edge member is parallel to the axis of the rollers.

This instrument is used by placing it on a sheet of drawing paper in the desired location and then drawing a straight line along the straight-edge. Parallel lines then can be drawn by simply placing a finger on the head of screw 14 and moving the instrument forward or backward to the next desired location. Only the front edge of the straight-edge member will engage the paper because the rollers will hold the bottom of that member and the bottom of the base plate off the paper as shown in FIG. 3. Since the two rollers are very narrow and must turn in unison because they are rigidly connected, the instrument will move back and forth in a straight line and will not tend to deflect to one side or the other. When the instrument. reaches the location where another line is to be drawn, screw 14 is pressed down to cause the base plate and straight-edge member to seat flat on the paper as shown in FIG. 4. This is permitted because the leaf spring will flex and allow the rear end of the base plate to move down when the screw is pressed. With the instrument seated fiat on the paper, the instrument is steady while a line is being drawn along its front edge. To further insure against slippage, a sharp point or the like may project from the bottom of the base plate to penetrate the paper slightly. This point can be on the lower end of a screw 17 that is threaded in a hole in the plate and that is held in any desired vertical position by a lock nut 18, or it can be molded in place.

In order to form a lettering slot, extension plates 20 can be secured to the top of the straight-edge strip at its opposite ends. These plates project longitudinally from the ends of the strip and are provided with notches 21 and 22, one of which perferably extends laterally and the other forward. A second straight-edge member 23 can be placed in front of the first one. The second member is longer than strip 11 and has rearwardly extending end portions that extend beneath the extension plates 20, so the member is U-shaped. Each end portion is provided with a slot 24 in which a screw 25 is slidably mounted. A nut 26 is screwed on the upper end of each screw. These screws extend up through the notches of the extension plates so that the nuts can be screwed down against those plates to clamp the second straight edge member 23 in place. When the two straight-edge members are in engagement with each other as shown in FIG. 1, the front edge of the U- shape member 23 serves as the straight-edge of the instrument. By loosening nuts 26 and moving the U-shape member forward, a slot with parallel sides can be opened up between the two straight-edge members. This slot can be used for lettering.

The outer edges of the ends of the U-shape member 23 can be used for drawing lines at right angles to the front straight-edge. If desired, this member can be swung around to an angle with the first straight-edge member 11. In fact, member 23 could be made L-shape instead of U-shapes by omitting one of its rearwardly extending ends, but in such a case the connection between the two straight-edge members might not be as secure as otherwise, or a different type of connection might be required.

In the modification shown in FIGS. 6 to 8', the principle of the invention is the same but the construction is somewhat different. The base plate, straight-edge member, spring strip means, and axle support can all be molded in one piece from a suitable plastic. The base plate 31 may be much wider than in the first embodiment, but the straight-edge member 32 still projects from the opposite sides of the front of the plate. The spring strip means, in the form of a pair of leaf springs 33, are disposed at opposite sides of the base plate. The rear end of each spring is integral with the top of a post 34 on the rear corner of the base plate. The front end of each spring is provided with a downwardly extending integral bearing 36, and an axle 37 extends through the two bearings. The projecting ends of the axle are threaded and narrow rollers 38 are screwed onto the ends and up against the bearings so that there is no end play of the axle. The major portion of the axle between the two springs is enclosed and shielded by an inverted channel 39 made integral with the base plate. The center of this channel may be provided with a small opening 40 indicating the point at which a finger should be applied for rolling the instrument forward or backward.

The front edge of the straight-edge member is parallel to the axis of the rollers. This edge may be used to guide a pencil or pen in drawing a straight line or a second straight-edge strip 41 of uniform width can be held against it by pins 42 rigidly mounted in bosses 43 on top of the strip. The pins extend back through sleeves 44 mounted on the first straight-edge member 32. These sleeves are provided with vertical necks 45, in which setscrews 46 are threaded. The screws can be turned down against the pins in the sleeves to hold the straight-edge strip 41 against the member 32 as shown, or to hold it any desired distance from the first strip so as to provide a lettering slot between them.

As with the first embodiment of the invention, this instrument is moved forward or backward by merely pushing or pulling it with a finger engaging the channel member at its central opening 40. The rollers normally space all but the front edge of the instrument from the supporting surface and therefore allow it to move back and forth very easily. When the straight-edge is in the desired position, the finger that moves the instrument presses down to seat the base plate and the straight-edge member or members flat upon the supporting surface. This downward movement is permitted by the flexing of the leaf springs. As soon as finger pressure is released from the instrument, the springs 'will lift the base plate free of the supporting surface again.

I claim:

1. A drafting instrument comprising a stiff base plate having front and rear ends, spring strip means connected with the back end of the plate and extending forward over it, an axle above said plate extending across the front of the spring strip means and projecting laterally therefrom, means fastening the axle to the spring strip means, rollers mounted on the ends of the axle and normally extending slightly below the base plate for spacing it from a surface supporting the rollers, a straight-edge member extending across the front end of the plate and laterally 4 therefrom, the back of the straight-edge member being joined to the plate, the bottoms of the base plate and straight-edge member normally sloping downward and forward, and said spring strip means allowing said plate and straight-edge member to be pressed down fiat on the supporting surface.

2. A drafting instrument according to claim 1, including means extending from said plate upwardly beside said axle and above it for receiving the downward pressure of a finger to press the plate down.

3. A drafting instrument according to claim 1, including means for detachably connecting said straight-edge member to said plate.

4. A drafting instrument according to claim 1, including a second member in front of said straight-edge member and having a front edge parallel to the front edge of the straight-edge member, an end of said second member having an edge perpendicular to its front edge extending rearwardly therefrom, and means detachably connecting said end of the second member to the adjoining end of said straight-edge member.

5. A drafting instrument according to claim 1, in which said spring strip means is a leaf spring, and said plate and spring are midway between the ends of said straight-edge member.

6. A drafting instrument according to claim 1, in which said spring strip means is a leaf spring spaced above said base plate in generally parallel relation with it, and said plate and spring are midway between the ends of said straight-edge member.

7. A drafting instrument according to claim 1, including a sharp member projecting slightly from the bottom of said plate.

8. A drafting instrument according to claim 1, in which said spring strip means are two laterally spaced leaf springs, and a shield covers said axle between said springs and is secured to said base plate.

9. A drafting instrument according to claim 1, including a second member in front of said straight-edge member and having a front edge parallel to the front edge of the straight-edge member, a pin projecting rearwardly from the opposite ends of said second member, sleeves mounted on the opposite ends of said straight-edge member and slidably receiving said pins, and setscrews connected to said sleeves for pressing against the pins therein.

References Cited UNITED STATES PATENTS 652,832. 7/ 1900 Carmical 33-109 1,005,218 10/1911 Holmes 33109 FOREIGN PATENTS 162,002 1/1949 Austria. 292,378 6/ 1928 Great Britain.

HARRY N. HAROIAN, Primary Examiner 

